Add request cpu time prometheus metrics

lib/gitlab/metrics/system.rb

@@ -63,6 +63,19 @@ module Gitlab
       def self.monotonic_time
         Process.clock_gettime(Process::CLOCK_MONOTONIC, :float_second)
       end
+
+      def self.thread_cpu_time
+        return unless defined?(Process::CLOCK_THREAD_CPUTIME_ID)
+
+        Process.clock_gettime(Process::CLOCK_THREAD_CPUTIME_ID, :float_second)
+      end
+
+      def self.thread_cpu_duration(start_time)
+        end_time = thread_cpu_time
+        return unless start_time && end_time
+
+        end_time - start_time
+      end
     end
   end
 end

lib/gitlab/metrics/transaction.rb

@@ -44,6 +44,10 @@ module Gitlab
         duration.in_milliseconds.to_i
       end
 
+      def thread_cpu_duration
+        System.thread_cpu_duration(@thread_cputime_start)
+      end
+
       def allocated_memory
         @memory_after - @memory_before
       end
@@ -53,12 +57,14 @@ module Gitlab
 
         @memory_before = System.memory_usage
         @started_at = System.monotonic_time
+        @thread_cputime_start = System.thread_cpu_time
 
         yield
       ensure
         @memory_after = System.memory_usage
         @finished_at = System.monotonic_time
 
+        self.class.gitlab_transaction_cputime_seconds.observe(labels, thread_cpu_duration)
         self.class.gitlab_transaction_duration_seconds.observe(labels, duration)
         self.class.gitlab_transaction_allocated_memory_bytes.observe(labels, allocated_memory * 1024.0)
 
@@ -142,6 +148,12 @@ module Gitlab
         "#{labels[:controller]}##{labels[:action]}" if labels && !labels.empty?
       end
 
+      define_histogram :gitlab_transaction_cputime_seconds do
+        docstring 'Transaction thread cputime'
+        base_labels BASE_LABELS
+        buckets [0.1, 0.25, 0.5, 1.0, 2.5, 5.0]
+      end
+
       define_histogram :gitlab_transaction_duration_seconds do
         docstring 'Transaction duration'
         base_labels BASE_LABELS

spec/lib/gitlab/metrics/transaction_spec.rb

@@ -27,6 +27,14 @@ describe Gitlab::Metrics::Transaction do
     end
   end
 
+  describe '#thread_cpu_duration' do
+    it 'returns the duration of a transaction in seconds' do
+      transaction.run { }
+
+      expect(transaction.thread_cpu_duration).to be > 0
+    end
+  end
+
   describe '#allocated_memory' do
     it 'returns the allocated memory in bytes' do
       transaction.run { 'a' * 32 }